The present invention relates to a bag inflatable by gas under pressure and fillable with a liquid for closing off a mine gallery, especially for use to prevent spreading of underground explosions, in which the bag after inflation has a cylindrical or half cylindrical cross section with curved end faces and is provided at an upper portion thereof with an overpressure valve and on one end face thereof with tubes communicating with the interior of the bag for filling the latter with the pressure gas, respectively the liquid.
Flexible bags to be filled with water or other fire extinguishing fluids to provide the miners with a preliminary protection during suddenly occurring underground fires or explosions are already known from the German Offenlegungsschrift 2,136,346. Such bags filled with liquid act during an explosion against the dynamic explosion pressure and reduce, as experiments have shown, the explosion pressure wave practically to zero. This, however, necessarily leads to a bursting of a bag. The quenching liquid emanating from the bursting bag will cool the explosion flame, however, this will not completely exclude that the miners will be exposed to subsequent explosions.
Explosion-resistant dams which consist of wooden sheeting which is filled with a quickly hardening solid material are also already known. Due to their high weight, they are adapted to withstand explosions. The necessary time for erecting such dams is, however, considerable and this may entail that during rapid spread of an underground fire, whole sections of a mine gallery will have to be abandoned.